@Dark Elegance Xx,
Hello. If you are still planning on finishing that story, I usually end my stores with these elements;
1) Sad twist
2) Dramatic referencing to earlier parts/characters
And it is always great to keep in mind the small things before in the story, and how you expect the reader to read it. Because small things can make a big difference. More specifically, I would suggest Ben causes the main character to drown, but on accident. She dies thinking it was on purpose, and is angry. As a ghost she seeks out revenge, but don't make it obvious. This way you can make a part two, or leave it at a cliff hanger.
(Also, just you know in Ben's original story, he died at 11...)